Recently, with increasing development of information industries, handheld devices such as notebook computers, personal digital assistants or remote controllers are widely used in many instances. In a case that a handheld device is used in a dim environment, the numbers and characters marked on the keys of the keyboard of the handheld device can not be clearly visible. In other words, the dim environment becomes hindrance from operating the keyboard. In addition, if the keyboard is used in the dim environment, the user is readily suffered from vision impairment. For solving these drawbacks, a luminous keying module has been disclosed. The luminous keying module may be used in the dim environment in order to enhance the applications thereof. Moreover, by changing the arrangement of the luminous regions, the handheld device having the luminous keying module is more aesthetically-pleasing and thus the competiveness thereof is enhanced.
FIG. 1 is a schematic cross-sectional view illustrating a conventional luminous keying module of a handheld device. FIG. 2 is a schematic partial perspective view illustrating a circuit board used in the luminous keying module of FIG. 1. Please refer to FIGS. 1 and 2. From bottom to top, a circuit board 11, an elastic layer 12, a light guide plate 13 and a keying layer 14 of the luminous keying module 1 are sequentially shown. In addition, plural light-emitting elements 15 are arranged beside the light guide plate 13. A circuit pattern 113 including plural membrane switches 111 and plural silver paste conductor lines 112 is formed on the circuit board 11. Each of the membrane switches 111 comprises a first conductive part 1111 and a second conductive part 1112. The first conductive part 1111 and the second conductive part 1112 are separated from each other.
Moreover, the elastic layer 12 has plural elastic bulges 121 corresponding to the plural membrane switches 111. A conductive structure 122 is printed on a bottom surface of each elastic bulge 121. The keying layer 14 has plural keycaps 141 corresponding to respective elastic bulges 121. Each conductive structure 122 and the corresponding membrane switch 111 are separated from each other by a spacing interval D1. The light guide plate 13 has plural perforations 131 corresponding to respective elastic bulges 121. The plural elastic bulges 121 are penetrated through respective perforations 131. When any keycap 141 is pressed down by a user, the corresponding elastic bulge 121 is pushed and compressed by the keycap 141. As the elastic bulge 121 is moved downwardly, the corresponding conductive structure 122 is contacted with the corresponding membrane switch 111. Under this circumstance, the first conductive part 1111 and the second conductive part 1112 are electrically connected with each other, so that the circuit board 11 generates a corresponding key signal. Whereas, when the depressing force exerted on the keycap 141 is eliminated, an elastic force provided by the compressed elastic bulge 121 is acted on the keycap 141. Due to the elastic force, the elastic bulge 121 is returned to the original shape. Correspondingly, the keycap 141 is moved upwardly and returned to its original position.
Moreover, the light guide plate 13 has plural light-guiding dots 132 for collecting and scattering light beams. The locations of the plural light-guiding dots 132 are determined according to the locations of the plural keycaps 141. After the light beams are incident into the light guide plate 13, the light beams by the light-emitting element 15 are diffused within the light guide plate 13. Due to the ink properties of the plural light-guiding dots 132, the light beams that are projected to the light-guiding dots 132 will be scattered upwardly or downwardly. The portion of the light beams that are scattered upwardly will be directed to the keycaps 141. In such way, the luminous keying module 1 has the luminous function.
However, the conventional luminous keying module 1 still has the following drawbacks.
Firstly, since a portion of the light beams projected to the light-guiding dots 132 are scattered downwardly, a part of the light amount is lost.
Secondly, please also refer to FIG. 3. FIG. 3 schematically illustrates a light path in the light guide plate of the luminous keying module of FIG. 1. Since the circuit pattern 113 comprises plural silver paste conductor lines 112 and these silver paste conductor lines 112 have functions of collecting and scattering the light beams, after the light beams L1 provided by the light-emitting elements 15 are introduced into the light guide plate 13, the light beams L2 passing through the silver paste conductor lines 112 of the circuit pattern 113 seem very bright. Since most of the silver paste conductor lines 112 are not aligned with the plural keycaps 141, the amount of the light beams to be directed to the keycaps 141 to illuminate the keycaps 141 are consumed by the silver paste conductor lines 112. That is, although the light beams L1 should be mostly directed to the keycaps 141 according to the original design, the silver paste conductor lines 112 may consume the amount of the light beams L2 because of the characteristics of the silver paste conductor lines 112. Consequently, only the light beams L3 are retained to be utilized by the light guide plate 13. Under this circumstance, the plural keycaps 141 of the luminous keying module 1 fail to be effectively illuminated.
Thirdly, since the light guide plate 13 has plural perforations 131, the light-guiding function of the light guide plate 13 is discontinuous. That is, when the light beams from the light-emitting elements 15 are incident into the light guide plate 13, the light beams are blocked by the perforations 131. Under this circumstance, the illuminating efficacy of the luminous keying module 1 is impaired. For increasing the luminance of the luminous keying module 1, it is necessary to increase the number of the light-emitting elements 15. The additional light-emitting elements 15 increase the fabricating cost of the luminous keying module 1.
Fourthly, since the luminous keying module 1 has too many components in a staked arrangement, it is difficult to reduce the overall thickness of the luminous keying module 1.
From the above discussions, the light utilization of the conventional luminous keying module of a handheld device is usually unsatisfied.